using System;

var now = DateTime.Now;
var dayOfWeek = now.DayOfWeek.ToString();
//in version 11:
var json = $"""
    {
        "Date" : "{{now.ToString("yyyy-MM-dd")}}",
        "DayOfWeek" : "{{dayOfWeek}}"
    }
    """
;

Console.WriteLine(json);
//prints:
//{
//    "Date" : "2024-09-11",
//    "DayOfWeek" : "Wednesday"
//}